A retrospective search for bovine respiratory syncytial virus (BRSV) antigens in histological specimens by immunofluorescence and immunohistochemistry

Abstract

Bovine respiratory syncytial virus (BRSV) has been only sporadically identified as a causative agent of respiratory disease in Brazil. This contrasts with frequent reports of clinical and histopathological findings suggestive of BRSV-associated disease. In order to examine a possible involvement of BRSV in cases of calf pneumonia, a retrospective search was performed for BRSV antigens in histological specimens submitted to veterinary diagnostic services from the states of Rio Grande do Sul and Minas Gerais. Ten out of 41 cases examined (24.4%) were positive for BRSV antigens by immunohistochemistry (IPX). Eight of these cases (19.5%) were also positive by indirect immunofluorescence (IFA), and 31 cases (75.6%) were negative in both assays. In the lungs, BRSV antigens were predominantly observed in epithelial cells of bronchioles and less frequently found in alveoli. In one case, antigens were detected only in the epithelium of the alveolar septae. The presence of antigen-positive cells was largely restricted to epithelial cells of these airways. In two cases, positive staining was also observed in cells and cellular debris in the exudate within the pulmonary airways. The clinical cases positive for BRSV antigens were observed mainly in young animals (2 to 12 month-old) from dairy herds. The main microscopic changes included bronchointerstitial pneumonia characterized by thickening of alveolar septae adjacent to airways by mononuclear cell infiltrates, and the presence of alveolar syncytial giant cells. In summary, the results demonstrate the suitability of the immunodetection of viral antigens in routinely fixed tissue specimens as a diagnostic tool for BRSV infection. Moreover, the findings provide further evidence of the importance of BRSV as a respiratory pathogen of young cattle in southeastern and southern Brazil.

Bovine respiratory disease associated with Histophilus somni and bovine respiratory syncytial virus in a beef cattle feedlot from Southeastern Brazil

“…Moreover, this is one of the few studies done in Brazil that has effectively investigated the infectious agents associated with BRD in beef cattle feedlots; we have previously demonstrated H. somni and BoHV-1 associated with respiratory disease in a beef cattle feedlot (HEADLEY et al, 2014), and multiple infectious agents were associated with BRD in dairy cattle (OLIVEIRA, 2014). Although other groups only investigated and confirmed the participation of BRSV in cattle reared in feedlots (BRASIL et al, 2013) and extensively (DRIEMEIER et al, 1997;FLORES et al, 2000) from diverse regions of Brazil, it is rather likely that other infectious disease pathogens associated with BRD might have been identified if these were investigated. Nevertheless, these results are encouraging since the infectious agents thus far identified in feedlot cattle from Brazil with BRD are similar to agents described in North America (GAGEA et al, 2006;GRIFFIN et al, 2010;FRANCOZ et al, 2015) and Australia (CUSACK et al, 2003), where the economic setbacks of respiratory disease on feedlot cattle is been intensively investigated.…”

“…We have theorized that H. somni might be a threat to beef cattle feedlots due to the continual diagnosis of this pathogen in respiratory (HEADLEY et al, 2014), reproductive (HEADLEY et al, 2015b), systemic (HEADLEY et al, 2013), and neurological (HEADLEY et al, 2015a) disease syndromes in cattle from different geographical regions of Brazil. Further, BRSV was associated with BRD in several herds from the state of Rio Grande do Sul, Southern Brazil (DRIEMEIER et al, 1997;BRASIL et al, 2013), while a retrospective study identified antigens of BRSV in cattle with bronchointerstitial pneumonia from Southern and Southeastern Brazil (FLORES et al, 2000). In addition, a recent study has demonstrated the participation of multiple infectious agents with the development of BRD in a dairy cattle herd from Paraná state, Southern Brazil (OLIVEIRA, 2014).…”

Characterization of bovine respiratory syncytial virus isolated in Brazil

“…Recent studies have demonstrated the presence of BRSV antibodies in numerous serum samples, as well as viral antigens in histological specimens used for the diagnosis of bovine infec- tions in the south and southeast regions of the country (6)(7)(8)(9). A serological investigation was performed with 864 serum samples from 65 different farms located in the southern Brazilian states, using serum neutralization test (SNT) and enzyme-linked immunosorbent assay (ELISA), and the clinical history was analyzed.…”

“…In former studies with samples from autopsied animal tissues, the difficulty in obtaining these free and infective viruses seemed to be greater due to the time elapsed between death, autopsy and inoculation in the cell cultures (6,9). Furthermore, it is easier to obtain tissue samples from animals autopsied during the acute phase of the disease (10).…”

Dot-enzyme linked immunosorbent assay as an alternative technique for the detection of bovine respiratory syncytial virus (BRSV) antibodies

“…Very little is known about the significance of BRSV in Brazil. Recent studies have shown BRSV antibodies in numerous serum samples and BRSV specific antigens have been detected in histological specimens of bovines submitted to veterinary diagnosis in the southern and southeastern regions of Brazil [4,9,11,13].…”